i accidentally ate my sister's ice cream and shared the story to my friends, he joked that i should write a Shakespeare styled poem about me apologizing to her so now i'm here
It's not that easy. Words can't change their accent. You have the word down not accented in your top example, but moving into an unaccented space in the second example. The word is either accented it or it isn't. It doesn't change just because you switched positions. If the first one is wrong because of hallway, then the second one is wrong because of down.
It's not even correct to say that the first one is not in iambic pentametre. Just say everything correctly and in any case form elisions from doubled soft syllables. See how liberal Shakespeare was with Hamlets soliloquy, it was definitely not as strict as '10 syllables; every second syllable must be stressed', even the very first line of it has 11 syllables.
